Network-AI: EnvironmentManager.backup() follows symlinked directories and copies files outside the environment root into backups

Network-AI is a TypeScript/Node.js multi-agent orchestrator. Prior to version 5.12.2, `EnvironmentManager.backup()` recursively collects files using `_collectBackupFiles()`. `_collectBackupFiles()` uses `statSync(full)`, which follows symlinks. If `data/<env>` contains a symlink to a directory outside the environment root, backup recursion follows the symlink and copies external files into `data/<env>/.backups/<backupId>/`. An attacker who can place a symlink under the environment data directory can cause backup operations to disclose files outside the environment root into backup artifacts. The issue is fixed in v5.12.2. `_collectBackupFiles()` now uses `lstatSync` instead of `statSync` and skips any entry where `isSymbolicLink()` is true. Symlinks are never traversed, so `backup()` can no longer follow a link out of the environment root and copy external files into a backup artifact.